Method and system implementing user-centric gesture control

ABSTRACT

A user-centric method and system to identify user-made gestures to control a remote device images the user using a three-dimensional image system, and defines at least one user-centric three-dimensional detection zone dynamically sized appropriately for the user, who is free to move about. Images made within the detection zone are compared to a library of stored gestures, and the thus identified gesture is mapped to an appropriate control command signal coupleable to the remote device. The method and system also provides of a first user to hand off control of the remote device to a second user.

RELATION TO CO-PENDING APPLICATION

Priority is claimed from U.S. provisional patent application Ser. No.61/217,355 filed on May 29, 2009, entitled User-Centric Gesture Control.

FIELD OF THE INVENTION

The invention relates generally to methods and systems usable with adepth imaging system to enable a user to remotely control a device, andmore specifically to such methods and systems enabling remote controlthrough recognition of user gestures defined within user-centricfour-dimensional (x, y, z, time) space.

BACKGROUND OF THE INVENTION

Remote control of devices including video devices has evolved from useof IR or acoustic type remote controls held by a user to controltelevision sets and the like equipped with IR or acoustic recognitionsystems, to imaging systems that attempt to image the user in two orpreferably three dimensions to recognize movements or gestures intendedto control the television or other device. FIG. 1 depicts a genericprior art system 10 in which a device 20, here a television, is remotelycontrolled by a user 30, whose head is shown from the back in thefigure. System 10 includes at least one imaging system, here a camera,e.g., 40-1, 40-2, coupled electronically to a signal processor unit 50,whose processor output can control operation of television 20.

The field of view of camera(s) 40-1, 40-2 encompasses at least a portionof three-dimensional space in which the user can make gestures, forexample with at least one hand (e.g., left hand 60) to controltelevision 20. If conventional RGB or gray scale images are acquired,then typically two spaced-apart cameras 40-1, 40-2 will be employed.Ideally, allowable gestures would include moving user hand(s) towards oraway from television 20, but RGB or gray scale cameras, including a pairof such cameras disposed stereographically, might not correctly discernsuch movement relative to system 10. RGB or gray scale cameras arereadily confused by ambient lighting including light generated by thetelevision display itself, by the clothing of the user, e.g., a whitehand in front of a user's white shirt, by reflectivity of objects withinthe field of view, etc.

Various imaging systems that seek to acquire three-dimensional images ofa user creating gestures intended to control a device are known in theart. Some three-dimensional imaging systems use so-called paralleltechniques and may include two-cameras, such as shown in FIG. 1. Varioustwo-camera implementations include so-called passive stereo in which asparse depth map is created in which only some sensor pixels in thedepth map actually contain depth information. Another two cameraapproach to acquiring depth images is texture patterned stereo, in whichthe depth system creates a pattern that generates texture but does notencode depth information. If a speckle-like randomly patternedillumination is used, there may be sufficient texture in the imagedscene to enable creation of a dense depth map. Yet another type of twocamera imaging system is depth-coded patterned stereo, in which apatterned Illumination source codes depth information and can provide adense depth map. A problem common to many two-camera systems isocclusion and so-called correspondence ambiguity. It can be challengingto combine the imagery acquired by two spaced-apart cameras tounambiguously determine depth in an imaged scene.

Some parallax imaging methods use a single camera with a patternedsource of illumination. So-called structured light systems can create anear-far qualitative depth map, but may suffer from an imprecisebaseline. PrimeSense, an Israeli company, markets such structured lightsystems. So-called active stereo single camera systems can acquire adense depth map with a precise baseline.

Another and somewhat superior method of three-dimensional imaging usestime-of-flight (TOF) information to create a dense depth map. Canesta,Inc. of Sunnyvale, Calif. (assignee herein) has received several dozenU.S. patents directed to methods and systems that can acquire true depthimages. Exemplary such U.S. patents received by Canesta, Inc. includeU.S. Pat. No. 6,323,942 (2001) CMOS-Compatible Three-Dimensional ImageSensor IC, U.S. Pat. No. 6,515,740 (2003) Methods for CMOS-CompatibleThree-Dimensional Image Sensing Using Quantum Efficiency Modulation,U.S. Pat. No. 6,522,395 (2003) Noise Reduction Techniques Suitable forThree-Dimensional Information Acquirable with CMOS-Compatible ImageSensor ICs, U.S. Pat. No. 6,614,422 (2003) Methods for EnhancingPerformance and Data Acquired from Three-Dimensional Image Systems, U.S.Pat. No. 6,674,895 (2004) Methods for Enhancing Performance and DataAcquired from Three-Dimensional Image Systems, U.S. Pat. No. 6,678,039(2004) Method and System to Enhance Dynamic Range Conversion Useablewith CMOS Three-Dimensional Imaging, U.S. Pat. No. 6,710,770 (2004)Quasi-Three-Dimensional Method and Apparatus to Detect and LocalizeInteraction of User-Object and Virtual Transfer Device, U.S. Pat. No.6,906,793 (2005) Methods and Devices for Charge Management forThree-Dimensional Sensing, U.S. Pat. No. 7,151,530 (2006) System andMethod for Determining an Input Selected by a User Through a VirtualInterface, U.S. Pat. No. 7,176,438 (2007) Method and System toDifferentially Enhance Sensor Dynamic Range Using Enhanced Common ModeReset, U.S. Pat. No. 7,212,663 (2007) Coded-Array Technique forObtaining Depth and Other Position Information of an Observed Object,U.S. Pat. No. 7,321,111 (2008) Method and System to Enhance DifferentialDynamic Range and Signal/Noise in CMOS Range Systems Using DifferentialSensors, U.S. Pat. No. 7,340,077 (2008) Gesture Recognition System UsingDepth Perceptive Sensors, U.S. Pat. No. 7,352,454 (2008) Methods andDevices for Improved Charge Management for Three-Dimensional and ColorSensing, and U.S. Pat. No. 7,507,947 (2009) Method and System toDifferentially Enhance Sensor Dynamic Range Using Enhanced Common ModeReset.

Typically a TOF system emits optical energy and determines how long ittakes until at least some of that energy is reflected by a target objectand arrives back at the system to be detected by an array of pixeldetectors. If t₁ denotes roundtrip TOF time, then the distance betweentarget object and the TOF system is Z1, where Z1=t₁·C/2, where C isvelocity of light. Most Canesta TOF systems are phase-based and compareshift between phase of the modulated emitted optical energy and phase ofthe reflected energy in determining depth Z. Canesta TOF systems areoperable with or without ambient light, have no moving parts, and can bemass produced using CMOS techniques. Phase-based TOF systems are alsobelieved available from PMD Technology of Siegen, Germany, Mesa Imaging,AG of Zurich, Switzerland, and possibly Optrima NV of Brussel, Belgium.

Another method of TOF systems that does not measure phase shift is theshutter type TOF system. The shutter may be an active optic device,perhaps GaAs as developed by 3DV Corp. of Israel, or perhaps anelectronic shutter, e.g., CMOS, as developed by TriDiCam GmbH ofGermany.

Three-dimensional imaging may be accomplished without using a parallelmethod, or a TOF method, for example by using spaced-apart cameras fromwhose images relative or inferred depth Z information may be had. Suchsystems are believed to be developed by XTR 3D Company of Israel.Alternative methods for inferring depth may rely upon camera motion,so-called structure-from-motion analysis, but these methods are notdeemed sufficiently fast for use in a gesture recognition system. Othermethods for inferring depth include so-called depth-from-focustechniques in which the focal plane of an imaging camera is changed tocreate a depth map. However such techniques may not be adequately fastor accurate for real-time gesture recognition.

Having briefly reviewed the various methods known in the art forobtaining depth or Z images, consider now an exemplary prior artapproach to gesture recognition with reference to FIG. 1. Assume thatsystem 10 include a display 20 whose characteristic(s) a user 30 willattempt to influence or alter using user-made gestures that are imagedhere by spaced-apart cameras 40-1, 40-2. System 10 is what may be termeddevice-centric and typically requires closed-loop visual feedbackbetween user 10 and a portion of what is displayed on television system20. FIG. 1 shows, for example, a cursor 70 near the upper left corner onthe television display, and also shows a double-arrow icon 80 near theright edge of the television display. In this example, if the user cancause cursor 70 to move to the right, in the direction of phantom cursor70′, and overlie the upper or lower portion of arrow 80, the user canthus cause an increase or decrease in the sound volume from television20.

In practice, system 10 will have pre-defined several gestures that theuser will know a priori. For example, to move cursor 70 to the right,the user may move the left hand to the right, as indicated by theposition of phantom hand 60′. Unfortunately doing so involves hand-eyecoordination between the displayed cursor on television 20, and theuser's hand position, as imaged by cameras 40-1, 40-2. The (x, y, z)coordinate system relied upon by system 10 is an absolute coordinatesystem that is defined relative to television set 20. This coordinatesystem means that the distance ΔX′ through which the user's hand must bemoved to move the cursor a distance ΔX on the television display is notconstant. Thus, if the user is say 8′ (2.5 m) away from the televisionset, distance ΔX′ will be substantially greater than if the user weresay 4′ (1.25 m) away from the television set. In addition to thisvarying distance sensitivity, the user must keep an eye on the cursorposition. In the example of FIG. 1, once the user moves the cursor tothe desired up or down portion of double arrow 80, the user might thenconfirm this selection, perhaps by moving the hand in the direction ofthe television screen. Having thus executed the desired correction tothe television volume, system 10 can automatically remove both thecursor and double arrow from the television display. If the user laterwishes to make some other adjustment, perhaps to change channels ontelevision 20, the user will make some other gesture known to system 10,and the cursor and other relevant icon(s) or images will appear on thetelevision screen.

While device-centric systems such as described in FIG. 1 can work, moreor less, there is room for improvement. The necessity for hand-eyefeedback between the user and what is presented on the television screenmay not be desirable for all classes of users. Such feedback requiressome user training, e.g., how much hand movement will cause how muchscreen movement at what distance away from the screen. This need foruser training may arise because device-centric systems have variationsas the user changes position relative to the device that can affect theuser's feel for device control. For example, unless scaling is donecorrectly, an action that requires some subtle motion when the user isfar from the device can require large motions when the user is close tothe device. Unless addressed in some fashion, this scaled feedbackcharacteristic of some prior art systems can limit the type of usergestures that can reliably be recognized and acted upon.

Further, systems such as described in FIG. 1 are device-centric in thatthe three-dimensional coordinate system used by the system is definedrelative to the device, and not to the user. In some applications thedevice-centric nature of the system can result in ambiguous recognitionof what device control action was intended by a given user gesture. Forexample, a user gesture intended to increase the channel number shouldnot be misinterpreted as a user desire to increase the device volumesetting, etc.

What is needed is a remote control method and system that does notrequire hand-eye feedback between the user and the device beingcontrolled. Preferably such method and system would employ auser-centric relative coordinate system rather than an absolutedevice-centric coordinate system. Such method and system would free theuser from undue concentration upon the device screen to implement remotecontrol. Preferably such method and system should use three-dimensionalrather than two-dimensional image sensing, be intuitive to the user, andnot require substantial user training. Further such method and systemshould reliably recognize user gestures without ambiguousinterpretations. Gestures should be user-friendly to perform andremember, and should be defined to be unambiguous with good detectiondiscrimination characteristics. Preferably gestures should have nostate, e.g., nothing to remember, and should permit transitioning toanother gesture unambiguously.

The present invention provides such a remote control method and system.

SUMMARY OF THE PRESENT INVENTION

The present invention provides a remote control system and method thatis user rather than device centric, and thus relies upon localuser-centric coordinates rather than absolute, device or camera system,coordinates. A local environment or three dimensional zone ofinteraction is defined about the user, and can move as the user moves.The zone of interaction preferably is customized to the user in thesense that a large adult user will have a larger volume zone ofinteraction than a small child user. The user zone of interactiondefines the three-dimensional space in which gestures will be made anddetected. Defined user gestures made within the zone of interaction arerecognized by a preferably three-dimensional imaging system disposed onor about the device to be controlled. Preferably a small number, threeperhaps, three-dimensional hot spots or hot zones are defined withinthis larger zone of interaction. While user gestures are not confined tobe made solely within these hot spots, defining these hot spots enablesdetection of specific touch gestures. Such user gestures made within ahot spot preferably include at least “touching” the hot spot, anddrawing a shape (perhaps a circle or an arc) within the hot spot. Assuch, the system and method uses real-world coordinates and in terms offeedback can substantially de-couple the user from the device beingcontrolled. Because the local environment is defined relative to theuser, a form of metric confirmation exists such that user gestures madenear or far from the device are recognized without the need for userhand-eye coordination or user-device calibration. In embodiments of thepresent invention, preferably there is always at least a coarseone-to-one mapping between the user's local environment zone ofinteraction and the device display, which mapping is completelytransparent to the user.

A library of user friendly and intuitive gestures is pre-defined suchthat preferably no substantial user training is required to learn or toremember the gestures. The gestures themselves are defined so as to beunambiguous with good detection discrimination characteristics. Thedifferent gestures preferably have no state, e.g., are memory-less, andpreferably permit transitioning to another gesture unambiguously. Theuser need not even look at the device being controlled, e.g., atelevision, to make a gesture. Further, there is no compelling need fora cursor display, and there is no visual feedback that requires hand-eyecoordination. Good gesture recognition according to the presentinvention relies upon two detection properties, namely how well thethree-dimensional imaging system images the gesture, and how well theinventive method can discriminate the gesture from other potentialgestures, motions, or noise.

The system includes a preferably three-dimensional imaging system, suchas is known in the art, and a processor unit that includes memorystoring at least one software routine that defines a library of usergestures, and at least one algorithm for interpreting data from thethree-dimensional imaging system and assigning to the data anappropriate user gesture made within a hot zone in a region ofinteraction defined relative to the user. The processor unit preferablyincludes a processor that executes the algorithm and issues appropriatecommand signals to the device, e.g., television, being remotelycontrolled, although an external processor could instead be used. Assuch, the present invention implements what may be described as gesturesyntax, rather than mere gesture semantics.

In the event a user gesture cannot be uniquely identified by theprocessor unit, the system and method can display on the device choiceicons showing what is believed to be the current gesture, and asking forconfirmation, perhaps by the user moving a hand toward the device. Thethree-dimensional camera system may, but need not be, athree-dimensional TOF system. Such an imaging system readily enableshand or other object movements toward and away from the device to bereliably detected, regardless of shape or size or color or variations inambient light, including light from the television display itself.

Other features and advantages of the invention will appear from thefollowing description in which the preferred embodiments have been setforth in detail, in conjunction with their accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a generic prior art gesture recognition system in whichdevice-centric coordinates are used, and hand-eye coordination anddevice calibration are typically required on the part of the user,according to the prior art;

FIG. 2 depicts a user-centric gesture recognition system, according toembodiments of the present invention;

FIG. 3A-3G depict a library of exemplary gestures, according toembodiments of the present invention;

FIG. 4 is a flow chart depicting generic exemplary method stepsimplementing user-centric gesture control, according to embodiments ofthe present invention; and

FIG. 5 is a flow charge depicting generic exemplary method stepsimplementing user-centric gesture control, including further detailsconcerning handing off device control from one user to another user,according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 2 depicts a gesture recognition system 100, according toembodiments of the present invention. System 100 includes a preferablythree-dimensional imaging system 140, such as is known in the prior art,whose effective field of view encompasses a three-dimensional space inwhich at least one user may be present. For ease of illustration, system140 is depicted as a generic TOF system, although a non-TOF imagingsystem may instead be used. For example, a system employing multiplecameras might be used, as could other prior art three-dimensionalimaging systems, indicated generically by 140′. In FIG. 2, exemplary TOFsystem 140 emits optical energy (shown as phantom lines emanating awayfrom system 140) towards the user 30, and detects a fraction of thatoptical energy reflected by the user or other object(s) within the fieldof view. This reflected energy is depicted as phantom lines directedback to TOF system 140. Gesture recognition system 100 also includes aprocessor unit 150, which preferably includes memory 160, a processor ormicroprocessor 170, and various input/output circuitry 180. Outputsignals from processor unit 150 are coupled via path 190, to controltelevision or other device 20, responsive to user gestures that arerecognized by three-dimensional imaging system 100.

As indicated by the coordinate axes, the present invention uses worldcoordinates that are defined relative to user 30, rather than relativeto device 20 or system 100. System 100 defines, relative to user 30, alocal environment termed herein a three-dimensional zone of interaction200, which zone preferably is sized to the size of the user, and willmove as the user moves. User gestures, e.g., hand or arm gestures, madewithin the interaction zone are detected by system 100. Preferablywithin zone of interaction 200 a small number of three-dimensional hotzones 210, 220, 230 are defined, e.g., at least two and preferably threesuch zones. These hot zones are regions of three dimensional spacedefined within the larger interaction zone. In general, the user candraw shapes with one or more hands, e.g., perhaps a circle, an arc,etc., for detection within the interaction zone, However, embodiments ofthe present invention preferably look for occurrence of user touchgestures within the hot zones defined within the interaction zone. Insuch embodiments, the user can simply “touch” a hot zone, or make handmovement within a hot zone to commence or create a recognizable gesture.In practice, for a given user 30, zone of interaction 200 might haveexemplary dimensions on the order of perhaps 3′ (1 M) in left-to-rightwidth, 2′ (0.7 m) in height, and perhaps 2′ (0.7 m) in front-to-backdepth, although other dimensions could instead be defined. Each hot zone210, 220, 230 may occupy a shape, perhaps a sphere, with transversediameter of perhaps 2′ (0.7 m) within zone of interaction 200, althoughagain different dimensions could be defined. However for a physicallylarger user 30, all of these dimensions would automatically be scaledupward by system 100. Thus a user with long arms would interact with aphysically larger zone of interaction than a user with small arms, etc.An advantage of defining hot zones according to the present invention isto reduce occurrence of false detections, or detection of unintendedgestures.

Because the present invention uses a world coordinate system referencedto user 30, it is understood that if user 30 moves around, zone ofinteraction 200 and hot zones 210, 220, 230 can dynamically move andre-size with the current user position. Thus, if the user moves towardstelevision device 20 and then makes a gesture with one or more hands,the present invention will recognize the gesture. If the user then stepsbackwards or sideways and makes the same gesture, the present inventionwill still recognize the gesture, because the gesture is made within theinteraction zone, which is defined relative to the coordinate system ofthe user. Advantageously, a user's gestures can be recognized, whetherthe user is standing when making the gesture, sitting when making thegesture, as long as the user's gesture is made within thethree-dimensional imaging system field of view.

Furthermore, the velocity of the gesture may be coupled to the speed ofan action on the screen of device 20. For instance, if the user's righthand is moved from right to left, the device can respond by shifting asequence of images on the screen in the same direction. If the user'shand moves more rapidly, the images can shift more rapidly. If the userhand moves slowly, the images shift slowly. As noted, in the presentinvention velocity of the user's hand is determined in world coordinateswith respect to the user. In the example of the user's hand shifting adisplayed sequence of images, the coupling between the user action anddevice response will remain substantially constant regardless of thedistance between the user and the device.

As noted above, preferably system 100 detects gestures that areperformed inside the interaction zone, which can include regionsexternal to the hot zones. In addition to detecting user gestures tocontrol a device, embodiments of the present invention can also detectwhen a first user hands off device control to a second user.

User 30 is free to move about relative to device 20, and because (x, y,z) world coordinates are defined relative to the user, and thus zone ofinteraction 200 moves with the user, to dynamically define a localenvironment. It is intuitive for a user to be told he or she caninteract with a three-dimensional zone of interaction defined in frontof him or her, centered at perhaps shoulder level. It is also intuitivefor the user to be told that he or she can touch or draw shapes withinthree dimensional hot zones defined within the zone of interaction. Assuch, a user can make a gesture within the zone of interaction withouthaving to even look at device 20. This is easier for the user thanhaving to concentrate on device 20, to look perhaps for a cursor, andthen to manipulate a hand to move the cursor toward a desired region onthe television display. This desired elimination of hand-eye feedbackfurther contributes to the user-friendly manner in which gestures arecreated, without substantial training or hand-eye coordinationrequirements, according to the present invention. However, as will bedescribed, should a gesture not immediately be recognized by system 100,system 100 can temporarily display preferably three icons 240, 250, 260on device 20, which icons correspond to the preferably three hot zones210, 220, 230. In this embodiment, if there were N hot zones definedwithin interaction zone 200, then there would be a like number N ofdisplayed icons. Of course a different number of displayed icons and adifferent number of hot zones could be used. In FIG. 2, one of theseicons, perhaps center icon 250, can display what system 100 believes tobe the intended gesture or perhaps a target of the gesture. The targetof the gesture refers to an object on the display that is intended torespond to the gesture, perhaps an image in a sequence of images thatwill move in a direction and with a velocity responsive to motion of theuser's hand. In FIG. 2, adjacent icons, e.g., 240, 260, can give theuser the option to confirm or reject the thus-interpreted gesture, e.g.,by interacting with one of the preferably three hot zones 210, 220, 230.

It is useful at this juncture to briefly consider FIG. 3A-3G in which alibrary (stored or storable in memory 160) of exemplary gestures isshown. In FIG. 3A, a “swiping” gesture made at head level is defined as“turn on/menu”. In FIG. 3B, a movement of both open spaced-apart handstowards device 20 is defined as “pause/play”. Such forward motion isreadily detected by TOF camera system 140. By contrast, conventionaltwo-dimensional RGB or gray scale cameras such as used in the prior artsystem of FIG. 1 have a more difficult challenge with respect toreliably detecting such movements, and with respect to not being trickedby lighting, contrast changes, background colors, etc. Gestures such asshown in FIGS. 3B and 3C would be challenging for prior arttwo-dimensional RGB or gray scale systems to recognize properly becauseof their Z-direction movement.

In FIG. 3C, holding the open right hand briefly then moving forward candefine a “select” gesture. In other embodiments, a select gesture can bedefined in terms of the user's hand being present within a hot zone fora given amount of time, even without moving the hand within the zone.For example, a gesture may cause a menu to appear on television device20, and the user may be given an option, perhaps an icon of a DVD if itis desired to now view a DVD movie rather than continue to watch atelevision show. The user can “select” to go into the DVD movie mode byselecting the DVD icon. The user could then use a gesture, perhaps asshown in FIG. 2B, to start to play the DVD movie, or if the movie isplaying, to pause the movie, and so forth.

The appearance of icons on the television device is referred to hereinas a GUI event, and typically can occur to resolve potential ambiguityin a gesture. Thus, the “volume” icon 250 might appear as shown in FIG.2, to ask the user to confirm with a yes or no whether indeed the lastdetected gesture was intended to alter the device volume level. In suchinstance the user can motion left or right with a hand to select,respectively, “yes” or “no”, since the “yes” icon is to the left on thetelevision screen, and the “no” icon is to the right. In this example,the user's will move from one hot zone to a hot zone to the left, toindicate “yes”, or will move from one hot zone to a hot zone to theright to indicate “no”. Because this gesture is responsive to an iconquery on the television screen, the icon will not be interpreted as agesture to turn on the device, or to bring up a menu, as in FIG. 3A.System 100 can then confirm the user's selection, e.g., “yes”, perhapsby causing the “yes” icon to now be highlighted, or to appear to vibrateback and forth slightly. Thus, in the above embodiments, select gesturesmay be defined in terms of the user's hand, stationary or moving,remaining in a hot zone for a certain amount of time. It is understoodthat the present invention can be practiced without recourse to menusappearing on the device display, or indeed without requiring the user toview the system under control.

In FIGS. 3D and 3E, clockwise or counter-clockwise circular motion ofthe open right hand commands volume change. In FIG. 3F, downward motionof both hands closely-spaced with palms downward is “mute/unmute”, whilein FIG. 3G, moving both open hands toward each other defines a “turnoff” gesture. Of course more or fewer gestures could be defined.

According to embodiments of the present invention, to be unambiguouslyrecognizable by system 100, each gesture emphasizes syntax rather thansemantics. According to the present invention, a well defined gesturehas good detection and good discrimination properties. Good detectionmeans that three-dimensional depth imaging system 140 can readily imagethe gesture, and good discrimination means that the detected gesture isreadily discriminated from other gestures.

For example, in FIG. 3A, the hand swipe gesture is not readily confusedwith any of the other gestures shown, and thus has good discriminationproperties. But if several swipes to the right meant “turn on” andseveral swipes to the left meant “turn off”, there would be ambiguity.These gestures would be ambiguous because after completing one swipe tothe right, the hand would have to be returned from right-to-left torepeat the same gesture. But the act of returning from right-to-leftmight be interpreted as “turn off” rather than the return motionassociated with “turn on”. This example of a poorly defined gesture alsodemonstrates what is meant by the preferred requirement that a goodgesture be stateless or memory-less, e.g., it should not have an initialcondition. Thus in FIG. 3C or 3D, making continuous circular motion in aclockwise or counter-clockwise direction is stateless or memory-lessbecause there is no requirement for a starting position. Similarly inFIG. 3F, there is no requirement that the two hands commence theirdownward motion from a given starting point, and thus this gesture hasthe desired characteristic of being stateless or memory-less. Thus, manypresently preferred gesture movements might be said to be AC-coupled,unlike many DC-coupled gestures in the prior art. This use of theterminology AC-coupled or DC-coupled is analogous to an electronicsignal as viewed on an oscilloscope: the DC-coupled signal will have astatic DC offset, e.g., a starting point level, whereas the AC-coupledsignal has no offset. However the present invention is sufficientlyflexible to recognize even so-called DC-coupled gestures. Presentlypreferred gestures according to the present invention are not defined assub-sets of other gestures, although they could of course be so defined.Thus if one gesture is a full circular hand rotation, perhaps to commanddevice volume change, it could be potentially confusing to also have adifferent gesture that is a half-circle, e.g., a sub-set of the fullcircle gesture.

According to the present invention, gestures are disambiguated byassigning what might potentially be an ambiguous gesture to a singlefunction, e.g., the swipe gesture of FIG. 3A could be ambiguous if aswipe to the right defined one gesture, and a swipe to the left definedanother gesture. However the back-and-forth swipe gesture of FIG. 3Adefines a single gesture, here turn-on/menu. Note too that gesturesshould not include motions that a user might normally make, for example,applauding, scratching one's nose or head. These movements can occuralmost subconsciously and should not be used to define gestures,according to the present invention.

In many instances the user may be seated on a chair or couch, withanother person or persons sitting close by. Understandably system 100will define a single zone of interaction adjacent the user, and willignore motions, including gesture-like motions, made by other persons.However if the user wishes to transfer remote control over device 20 toanother person, a gesture may be defined to alert system 100 that a userin a different location, perhaps seated to the right of the originaluser, is about to take control. System 100 would then redefine the zoneof interaction and the hot spots within, relative to the new user. Atthis juncture, motions including gesture type motions made by theoriginal user will not be responded to, because they no longer occurwithin the relevant zone of interaction.

FIG. 4 depicts an exemplary algorithm such as can be stored in memory160 in system 100 (see FIG. 2) for execution by processor 170 (or otherprocessor) to implement gesture recognition, according to embodiments ofthe present invention. Initially system 100 will acquire several framesof data to image user 30, and to then define an interaction zone 200,and hot spots or hot zones 210, 220, etc. therein for the imaged user.At method step 300, the user makes a “start” or “turn-on” gesture, forexample as shown in FIG. 3A, and at step 310, system 100 acquires user20. At step 320, system 100 tracks the imaged user, which means that ifthe user moves about relative to the position of the controlled device20, system 100 can successfully image the user. Gesture recognitionaccording to the present invention is user-centric, not device-centric,and the user is free to move about relative to the position of device20.

At step 340, the system confirms that the imaged user is indeed beingtracked. If for some reason tracking is not occurring, an “ACQUIRE”command is used at module 330 and step 310 is repeated until the user isproperly acquired and tracked.

Once user tracking is confirmed, method step 340 passes off to step 350,and appropriately sized user-centric zones including hot zones aredefined for this user. As noted, a physically large user will havelarger volume zones defined than would be the case for a physicallysmall user. Acquired images of user 20 enable system 100 to approximatethe user's size and to cause step 350 to generate appropriately sizedthree-dimensional zone spaces in which gesture detection preferably willoccur.

At method step 360, acquired images of the user and user hands withinthe detection zones and hot zones are examined to detect user madegestures. As noted earlier, the preferred use of hot zones in whichtouch type gestures should be made tends to reduce false detection ofgestures, as well as ambiguous identification of detected gestures.

At method step 370, system 100 compares the detected gesture withcontents of a user gestures that have been previously stored, e.g., inmemory 160 in system 100. A best determination of the user gesture ismade, and this gesture is then mapped to appropriate command(s) forcontrolled device 20. For example, if the user gesture is determined tomean “increase volume level” for device 20, a method step 370 theappropriate electronic command signals to cause an increase in device 20audio volume level will be generated. These signals can be coupled todevice 20 via cable(s), or wirelessly, e.g., IR, Bluetooth, etc.

Having made the appropriate parameter change to operation of device 20,at method 380, system 100 will continue to image the user. If apredetermined amount of time lapses without detection of furthergestures, system 100 will look to see whether there is a new,substitute, user, perhaps positioned other than precisely where thepresent-former user was last positioned. If a new user is found, and itis determined that the new user is performing an “acquire me” gesture,the software in memory 160 being executed, e.g., by processor 170 (orother processor) will substitute the new user for the old user. But ifno new user is found, the old user will remain as the current user,whose continuing user gestures will be imaged and processed to controldevice 20.

FIG. 5 depicts a further exemplary algorithm such as can be stored inmemory 160 in system 100 (see FIG. 2) for execution by processor 170 (orother processor) to implement gesture recognition, according toembodiments of the present invention, and more particularly to implementa change in user control of device 20. As was the case with FIG. 4,system 100 initially acquires several frames of data to image user 30,and to then define an interaction zone 200, and hot spots 210, 210, etc.therein for user 20.

Similarly to what was described with respect to FIG. 4, at method step400, the user makes a “start” or “turn-on” gesture, and at method step410, camera system 140 acquires a frame of three-dimensional data thatincludes any user interaction within interaction zone 200. At step 420system 100 searches for an acquisition gesture. As was described withrespect to FIG. 4, the gesture preferably is identified by comparinggestures stored in library 160 with a just-acquired gesture, discernedfor example by processor 170 from data output from camera system 140. Ifan acquisition gesture is not acquired, the routine returns to step 410,to examine a next acquired frame of camera system data. Eventually aacquisition gesture will be acquired at step 420.

At this juncture step 430 is bypassed and at step 440, system 100examines the hot spots or hot zones 210, 220, 230, which act as segmentsof the interaction zone 200, to determine whether a touch gesture hasbeen detected. If detected, the user interface (UI) signals a “touch” or“hold” event, and the method branches to step 460 to test whethertracking of the user has been lost. Input to step 460 also includes theabsence of touch detection at step 440. If tracking has not been lost,step 460 branches to detection step 510. If a gesture is detected, themethod branches to step 520 and a user interface “command name” signalis issued. Step 530 tests to determine whether a stop command has beendetected, e.g., a stop gesture. If a stop command has been detected,then at step 540 system 100 will turn-off the application, in thisexample, television 20. But if test 530 determines that the gesture isnot a stop command, then the routine branches back to step 530, toexamine the next acquired frame of data from camera system 140.

Detection step 510 also outputs to step 550, which tests for thepresence of another user. Perhaps the first user has an errand to runand will pass control of device 20 to a second user. As noted, one candefine a gesture intended to alert system 100 to the transfer of remotecontrol command from one user to another user, perhaps a second personsitting next to the initial user. If it is not apparently time to searchfor another user, then step 510 branches back to step 530, and the nextframe of acquired data is examined. However if step 510 determines thatno gesture is detected and it is time to look for a new user, theroutine branches to step 480. If a new user cannot be determined, theroutine branches back to step 430, and data from the next acquired frameis analyzed. However if step 480 determines a new user is present, thenthe routine branches to step 490 and a signal UI acquisition gesture istested. Step 500 then retargets tracking.

In summary, it will be appreciated that user-centric gesture recognitionprovides many advantages over prior art techniques. Advantageously,embodiments using hot zones can reduce incidents of false gestureidentification and recognition. The present invention may be practicedwith a variety of prior art three-dimensional imaging systems 140,including without limitation Canesta, Inc. time-of-flight (TOF) systems.An advantage of such TOF systems is that overall system and methodreliability can be enhanced, as gesture recognition is not likely to betricked by user clothing colors, reflections, by ambient light, and thelike.

Modifications and variations may be made to the disclosed embodimentswithout departing from the subject and spirit of the invention asdefined by the following claims.

What is claimed is:
 1. A method implementing user-centric gesturerecognition enabling a user to remotely gesture-control a device, themethod comprising: disposing a three-dimensional imaging system whosefield of view encompasses a three-dimensional space in which at leastone user may be present, and recognizing a user when said user is withinsaid field of view; providing a gesture recognition system that definesa world coordinate system within said three-dimensional space based uponlocation of said user as determined by said imaging system, said worldcoordinate system moving with movement of said user; said gesturerecognition system defining relative to a current position of said useras determined by said imaging system a dynamically-sized and positionedthree-dimensional zone of interaction within which zone said user maymake at least one gesture; said gesture recognition system storing agesture library of at least one pre-defined gesture defined in threedimensions in said zone of interaction, the at least one pre-definedgesture useable to control said device; said gesture recognition systemrecognizing a gesture made by said user within said three-dimensionalspace and comparing said gesture to contents of said gesture library;upon finding a match between a recognized said user-gesture and contentsof said gesture library, outputting a signal useable to control saiddevice.
 2. The method of claim 1, further including defining at leastone sub-region within said three-dimensional zone of interaction,wherein presence of a portion of said user can be detected.
 3. Themethod of claim 1, wherein said gesture library stores at least onegesture selected from a group consisting of (i) a gesture signifyingdesire to acquire control of said device, (ii) a gesture signifyinghanding off remote control of said device from said user to a successoruser, (iii) a gesture made with one hand, (iv) a gesture made with twohands, and (v) a gesture causing a menu to be displayed on said device.4. The method of claim 1, further including causing said device to alerta user that a user-gesture may not have been correctly recognized bysaid gesture control system, and inviting said user to confirm improperrecognition of a gesture.
 5. The method of claim 4, wherein a user canconfirm improper recognition of a gesture by making a user movementwithin a sub-region defined within said three-dimensional zone ofinteraction.
 6. The method of claim 5, further including causing saiddevice to signal said user that improper recognition of a gesture mayhave occurred, and causing said device to provide an option for saiduser to at least confirm said improper gesture recognition.
 7. Themethod of claim 1, wherein said gesture library stores gestures that arestateless.
 8. The method of claim 1, wherein said three-dimensionalimaging system is a system selected from a group consisting of a (i)parallex-method imaging system, (ii) a time-of-flight imaging system,(iii) a phase-based time-of-flight imaging system, (iv) a shutter-basedtime-of-flight imaging system, and (v) a system using at least twospaced-apart cameras.
 9. The method of claim 1, wherein said deviceincludes at least one of (i) a display, (ii) a computer screen, (iii) acontrol panel, and (iv) a television receiver.
 10. A system enablinguser to remotely gesture-control a device using user-concentric gesturerecognition, the system comprising: a three-dimensional imaging systemwhose field of view encompasses a three-dimensional space in which atleast one user may be present, and recognizing a user when said user iswithin said field of view; a gesture recognition system, coupled to saidthree-dimensional imaging system, that defines a world coordinate systemwithin said three-dimensional space based upon location of said user asdetermined by said imaging system, said world coordinate system movingwith movement of said user; said gesture recognition system defining,relative to a current position of said user as determined by saidimaging system, a dynamically-sized and positioned three-dimensionalzone of interaction within which zone said user may make at least onegesture; and a gesture library including a plurality pre-definedgestures defined in three-dimensions in said zone of interaction, thegestures useable to control said device; said gesture recognition systemrecognizing a gesture made by said user within said three-dimensionalspace and comparing said gesture to contents of said gesture library;upon finding a match between a recognized said user-gesture and contentsof said gesture library, said gesture recognition system outputting asignal useable to control said device.
 11. The system of claim 10,wherein said gesture recognition system defines at least one sub-regionwithin said three-dimensional zone of interaction, wherein presence of aportion of said user can be detected.
 12. The system of claim 10,wherein said gesture library stores at least one gesture selected from agroup consisting of ((i) a gesture signifying desire to acquire controlof said device, (ii) a gesture signifying handing off remote control ofsaid device from said user to a successor user, (iii) a gesture madewith one hand, (iv) a gesture made with two hands, and (v) a gesturecausing a menu to be displayed on said device.
 13. The system of claim10, further including means for causing said device to alert a user thata user-gesture may not have been correctly recognized by said gesturecontrol system, and inviting said user to confirm improper recognitionof a gesture.
 14. The system of claim 13, wherein a user can confirmimproper recognition of a gesture by making a user movement within asub-region defined within said three-dimensional zone of interaction.15. The system of claim 14, further including means for causing saiddevice to signal said user that improper recognition of a gesture mayhave occurred, and causing said device to provide an option for saiduser to at least confirm said improper gesture recognition.
 16. Thesystem of claim 10, wherein said gesture library stores gestures thatare stateless.
 17. The system of claim 10, wherein saidthree-dimensional imaging system is a system selected from a groupconsisting of a (i) parallex-method imaging system, (ii) atime-of-flight imaging system, (iii) a phase-based time-of-flightimaging system, (iv) a shutter-based time-of-flight imaging system, and(v) a system using at least two spaced-apart cameras.
 18. The system ofclaim 10, wherein said device includes at least one of (i) a display,(ii) a computer screen, (iii) a control panel, and (iv) a televisionreceiver.
 19. A method implementing user-centric gesture recognitionenabling a user to remotely gesture-control a device, the methodcomprising: disposing a three-dimensional imaging system whose field ofview encompasses a three-dimensional space in which at least one usermay be present, and recognizing a user when said user is within saidfield of view; providing a gesture recognition system that defines aworld coordinate system within said three-dimensional space based uponlocation of said user as determined by said imaging system, said worldcoordinate system moving with movement of said user; said gesturerecognition system defining relative to a current position of said useras determined by said imaging system a dynamically-sized and positionedthree-dimensional zone of interaction within which zone said user maymake at least one gesture; said gesture recognition system storing agesture library of at least one pre-defined gesture useable to controlsaid device; said gesture recognition system recognizing a gesture madeby said user within said three-dimensional space and comparing saidgesture to contents of said gesture library; causing said device toalert a user that a user-gesture may not have been correctly recognizedby said gesture control system, and inviting said user to confirmimproper recognition of a gesture; and upon finding a match between arecognized said user-gesture and contents of said gesture library,outputting a signal useable to control said device.